1. Field of the Invention
This invention is directed to a load restraint system, and in particular to a safety adaptation to a load restraint system, for truck load winches, used for securing loads to railcars, flatbeds, automotive trucks and the like, providing a spring loaded safety winch, as OEM spring-loaded winches, and the conversion of existing winches.
2. Description of the Prior Art
The attachment of loads upon the beds of vehicles, for safe transportation, usually relies upon hold-down members, such as straps, chains, cables and the like that are passed over the load and secured to the sides of the vehicle, and there tensioned.
Tensioning of the hold-down members is usually effected by use of an in-situ, hand-operated winch to which one end of the hold-down member is attached.
The winch has a drum, about which an end of the hold-down member is wound. The drum has a capstan which is rotated by means of a lever or Tommy-bar that is inserted into a selected hole in the drum capstan, and the bar is then cranked angularly, to wind the hold-down member onto the drum, and to tension it.
The winch drum has a toothed ratchet portion at one end, adjacent the capstan, against which a ratchet pawl engages, to prevent reversed, overhauling rotation of the drum, which would otherwise result in the loss of the tension that is applied to the hold-down member. The use of nylon or other straps of suitable plastic may provide a degree of elasticity to the load restraint system. However, despite such elasticity, there is a distressingly frequent loss of tension in the hold-down member, due to settling of the load. This frequently results in shifting of the load, often with disastrous, frequently fatal consequences, more particularly for other road users. In cases where cables or chains are used as the hold-down member, the maintenance of tension is an even greater problem, due to an absence of elasticity and resilience in the hold-down member. Any settling of the load can lead to instantaneous loss of hold-down tension, which can then lead rapidly to shifting of the load. This particularly applies to loads such as logs.
This problem of inadequate security of load attachment is currently leading towards legislation proposing that, in the case of road trucks, for every three hours of travel or 150 miles covered, the vehicle shall be halted and the tension of the load securing hold-down members be checked. As there are usually a significant number of load members and their associated winches along the length of a modern, extended transport truck and/or trailer, such further checking involves the expenditure of considerable further time and effort on the part of the driver.
Added to this is the roadside hazard, affecting both passing traffic, in the event that there is no proper pull-off for the trucker to use, and more particularly involving the truck driver, who is particularly vulnerable beside the truck, when preoccupied in pulling down with full force against each of many winches, to re-tension the respective hold-down members.
A particularly adverse factor is the repetition, winch after winch, and time after time of the gross physical strain imposed upon the driver, particularly to the shoulders and back, the latter being especially vulnerable to injury. Instances of severe frontal injury and even death have occurred, usually due to kick-back or dislocation and forcible discharge of the loading bar from the winch.
The present invention has a preferred embodiment, applicable to OEM equipment and also having retro-fit capability, as an improvement to prior-existing load restraint winch systems, as used for securing an elongated load hold-down member in secured, tensioned relation across a load. The prior winch systems generally comprise a winch having a drum rotatable mounted in a frame; the frame having mounting notches, for sliding attachment of the winch to a winch track on the side of a truck; a manually operated capstan that receives an inserted loading (tommy) bar with which the capstan is rotated, to rotate the drum so as to wind-on and apply load-securing tension to the hold-down member; and a first ratchet-and-pawl means to prevent over-hauling reversal of the drum by the tensioned hold-down member. The drum portion of the winch to which the hold-down strap or cable is attached may comprise three parallel straight bars, spaced from, and parallel with the axis of rotation of the assembly. The load strap or cable is threaded between these bars, and wound about the bar assembly, which serves as the winch drum.
The preferred embodiment consists of spring-loaded tensioning means, mounted for rotation independently of the winch drum, and connected to the winch drum in driving relation by way of a second ratchet arrangement. The tensioning spring is loaded by means of a manual capstan, using the loading or tommy bar in the usual fashion. However, in the preferred embodiment, the tommy bar is pulled upwardly in order to load the spring, whereas the loading strap is normally first pulled down and tightened by the winch capstan, by cranking the tommy bar downwardly. In the unloaded condition of the spring, the pawl of the spring ratchet hangs clear of the ratchet, in a disengaged condition, leaving the drum of the winch free for normal use in the unwinding or winding-on of the load strap. The winch is thus used in its normal fashion, to apply and tension the load strap.
Then, upon upward loading of the spring by way of the spring capstan and inserted tommy bar, the pawl, being displaced arcuately upward with upward motion of the tommy bar, swings inward to engage the ratchet as the pawl moves upwardly. The spring assembly can be rotatably mounted upon an extension of the winch drum, lying outside of the winch frame, in the case of a short-frame winch; or within the frame of a long-frame winch, in coaxial relation with the winch drum.
Conversion of an existing winch to a spring-maintained safety model can be carried out by welding an extension cylinder to the winch drum. This extension cylinder carries a peripheral ratchet, to transfer torsional load from the spring to the winch drum.
The loading spring, in the form of a helical coil spring is mounted upon its cylinder, which can then be mounted in rotatable relation upon the extension cylinder of the winch drum. The spring cylinder carries the ratchet pawl that can engage the extension cylinder ratchet, when the spring is tensioned, to transfer torque loading to the winch drum. The rotatable spring-loaded tensioning means is secured to the winch drum in coaxial relation, and pre-tensioned to drive the winch drum in tension-maintaining relation with the hold-down member, in the event that the tension in the hold-down member should diminish.
The subject multi-coil spring is of predetermined stiffness, to provide a pre-determined winding take-up capacity to the load hold-down member, to absorb any slackening that may occur due to normal load settlement.
The subject spring-loaded tensioning means may include low-friction support bearings for the rotational parts.
The inner end of the spring is secured against rotation by way of a bracket mounted on the adjoining end face of the winch frame.
The axially outer end of the spring is secured to the spring capstan by way of an axially extending tang portion of the spring.
In use, this embodiment has the particular advantage that an operator/trucker can retain both hands upon the lever when loading the spring, as the pawl of the spring system engages the associated ratchet automatically under the effects of gravity as the pawl is displaced upwardly due to raising of the tommy bar.
The present invention thus provides a method of tensioning a load restraining hold-down device having a flexible hold-down member wound in tensioned relation upon a rotatable drum, including the steps of tensioning a driving spring, and connecting it in loading relation with the drum, and restraining the spring against reverse over-run, whereby, upon reduction in the tension of the hold-down member due to a change in load conditions, the drum is driven by the driving spring in a direction to maintain tension in the hold-down member, to restrain the load.